See, this is what happens when you're entirely self-educated. Try reading Battle Cry of Freedom: The Civil War Era for a little perspective on the inevitability of war, and why slavery would have existed today had it not been for Lincoln and Northern "aggression". Really boils down to the South not having any way of supporting themselves without slavery, economically and inextricably racially dependent on enslaving black Americans, something that continued for decades afterward in the form of sharecropping and only by WWII did a black middle class exist in any substantial numbers. Something pretty much zero American history scholars would agree would have been possible without the Civil War.
Books? Historical fact? Reality?
Nah. YouTube and Mises.org then, now, forever.
You see, the logical fact behind slavery is what you said here, without such free labor, the south would have been far less profitable, wealthy, and relevant. They knew it and wanted to keep an entire race subjugated in perpetuity. This is why they fought so hard for the 3/5ths compromise, they knew that if the Constitution were kept to only "Free" people, they would have been underrepresented and would have been forced to eventually de-slave, at the same time, they didn't want to pay the full might of taxes on that population.
As a result, the south was able to continue slavery for another 90 years and would have been able to continue it far longer had it not been for the north finally pressing the issue.
But hey, it was the north that wanted to keep it's mercantilism, not the south that wanted to keep slaves. This is what you get out of 3rd tier schooling and misguided educations perpetuated by libertopians who would like nothing more than return us to an agrarian wonderland of perfection.
That's the regressive agenda for you.